Monday, January 29, 2018

Creating a simple GTK+ ToDo application with Ruby

Lately I was experimenting with GTK and its Ruby
bindings and I decided to write a tutorial introducing this
functionality. In this post we are going to create a simple ToDo
application (something like what we created here with Ruby on Rails) using the gtk3 gem a.k.a. the GTK+ Ruby bindings.Note: The code of the tutorial is available at GitHub.

What is GTK+

GTK+, or the GIMP Toolkit, is a multi-platform toolkit for creating
graphical user interfaces. Offering a complete set of widgets, GTK+ is
suitable for projects ranging from small one-off tools to complete
application suites.

GTK+ was initially developed for and used by the GIMP, the GNU
Image Manipulation Program. It is called the “The GIMP ToolKit” so that
the origins of the project are remembered. Today it is more commonly
known as GTK+ for short and is used by a large number of applications
including the GNU project’s GNOME desktop.

Prerequisites

GTK+ version

Make sure you have GTK+ installed.
The OS in which I developed the tutorial’s application is Ubuntu 16.04 which has GTK+ installed by default (version: 3.18).
You can check yours with the following command:

dpkg -l libgtk-3-0

Ruby

You should have ruby installed on your system. I use RVM
to manage multiple ruby versions installed on my system. If you want to
go with that too, you can find instructions for installing the tool in
its homepage and for installing ruby versions (a.k.a. rubies) the related documentation page.
This tutorial is using Ruby 2.4.2. You can check yours using: ruby --version or via RVM with rvm list.

Glade

Glade is a RAD tool to enable quick & easy development of user
interfaces for the GTK+ toolkit and the GNOME desktop environment

We will use Glade to design the user interface of our application.
If you are on Ubuntu, install glade with:

sudo apt install glade

gtk3 gem

This gem provides the Ruby bindings for the GTK+ toolkit. In other
words, it allows us to talk to the GTK+ API using the Ruby language.
Install the gem via:

gem install gtk3

The application specs

We will build an application that:

it will have a user interface (desktop application)

it will allow users to set miscellaneous properties to each item (such as priority)

it will allow users to create and edit ToDo items

all items will be saved as files in the user’s home directory in a folder named .gtk-todo-tutorial

it will allow users to archive ToDo items

archived items should be put in their own folder archived

The application structure

gtk-todo-tutorial# root directory|--application|--ui# everything related to the ui of the application|--models# our models|--lib# the directory to host any utilities we might need|--resources# directory to host the resources of our applicationgtk-todo# the executable that will start our application

Let’s start!

Building the ToDo application

Initializing the application

Create a directory in which we will save all files that the application will need. As shown in the section above, I named mine gtk-todo-tutorial.
In there create a file named gtk-todo (that’s right, no extension) and add the following:

This is going to be the script that will start the application.
Note the shebang in the first
line. This is how we define which interpreter must be used to execute
the script under UNIX/Linux operating systems. This way, we don’t have
to use ruby gtk-todo but just the script’s name gtk-todo.
Don’t try it yet though because we haven’t changed the mode of the
file so as to be executable. To do so, type the following command in a
terminal after navigating to the application’s root directory:

chmod +x ./gtk-todo # make the script executable

Now from the console execute:

./gtk-todo # execute the script

Ta daaaaaaNotes

The application object we defined above and all of the GTK+
widgets in general, emit signals to trigger events. Once an application
starts running for example, it emits a signal to trigger the activate event. All we have to do is to define what we want to happen when this signal is emitted. We accomplished this by using the signal_connect
instance method and passing it a block whose code will be executed upon
the given event. We will be doing this a lot throughout the tutorial.

When we initialized the Gtk::Application object we passed two parameters:

com.iridakos.gtk-todo:
this is our application’s id and in general it should be a reverse DNS
style identifier. For more information about its usage and best
practices check here.

:flags_none: this is a flag defining the behavior of the application. In our case, we used the default behavior. Check here all the flags and the type of applications they define. You can use the Ruby equivalent flags as defined in Gio::ApplicationFlags.constants. For example, instead of using the :flags_none we could instead use Gio::ApplicationFlags::FLAGS_NONE

Suppose the application object we previously created (Gtk::Application) had a lot of things to do when the activate signal was emitted or that we wanted to connect to more signals. We would end up creating a huge gtk-todo script file making it hard to read/maintain. Time to refactor.
As described in the The application structure section, create a folder named application along with its sub-folders ui, models and lib.

In the ui folder we will place all files related to our user interface.

In the models folder we will place all files related to our models.

In the lib folder we will place all other files that don’t belong to either of the aforementioned folders.

We are going to define a new subclass of the Gtk::Application class for our application. Create a file named application.rb under application/ui/todo with the following contents.

Resources

At the beginning of this tutorial we said that we would use Glade to
design the user interface of the application. Glade actually produces xml
files with the appropriate elements and attributes that reflect what we
designed via its user interface. We somehow need to make use of these
files so that our application gets the UI we designed.
These files are resources for the application and the GResource API
provides a way for packing them all together in a binary file and
afterwards accessing them from inside the application with advantages as
opposed to manually having to deal with already loaded resources, their
location on the file system etc. Read more about the API here.

Describing the resources

First, we need to create a file describing the resources of the application. Create a file named gresources.xml and place it directly under the resources folder.

In this “description” we actually say: we have a resource which is located under the ui directory (relative to this xml file) with name application_window.ui.
Before loading this resource please remove the blanks. Thanks. Of
course this is not going to work now since we haven’t created the
resource via Glade yet. Don’t worry though, one thing at a time.Note: the xml-stripblanks directive will use the xmllint command to remove the blanks. In Ubuntu you have to install the package libxml2-utils to obtain it.

Building the resources binary file

In order to produce the binary resources file, we are going to use another utility of the GLib library called glib-compile-resources. Check if you have it installed with dpkg -l libglib2.0-bin. You should be seeing something like this:

ii libglib2.0-bin 2.48.2-0ubuntu amd64 Programs for the GLib library

If not, then install the package (sudo apt install libglib2.0-bin in Ubuntu).
Let’s build the file. We will add the code in our script so that the resources are getting built every time we execute it.
Change the gtk-todo script as follows.

#!/usr/bin/env rubyrequire'gtk3'require'fileutils'# Require all ruby files in the application folder recursivelyapplication_root_path=File.expand_path(__dir__)Dir[File.join(application_root_path,'**','*.rb')].each{|file|requirefile}# Define the source & target files of the glib-compile-resources commandresource_xml=File.join(application_root_path,'resources','gresources.xml')resource_bin=File.join(application_root_path,'gresource.bin')# Build the binarysystem("glib-compile-resources","--target",resource_bin,"--sourcedir",File.dirname(resource_xml),resource_xml)at_exitdo# Before existing, please remove the binary we produced, thanks.FileUtils.rm_f(resource_bin)endapp=ToDo::Application.newputsapp.run

and execute it. This happens in the console and it’s fine, we’ll fix it later on:

/.../gtk-todo-tutorial/resources/gresources.xml: Failed to locate 'ui/application_window.ui' in any source directory.

What we did:

added a require statement for the fileutils library so that we can use it in the at_exit call

defined the source and target files of the glib-compile-resources command

executed the glib-compile-resources command

set a hook so that before exiting the script (before the
application exits) the binary file gets deleted so next time it gets
build again

Loading the resources binary file

Ok, we described the resources, we packed them in a binary file. Now
we have to load them and register them in the application so that we can
use them.
This is so easy as adding the following two lines before the at_exit hook.

That’s it. From now on, we are able to use the resources from
anywhere inside the application (we’ll see how later on).
Well now the script fails since it can’t load the binary which is not
produced but…be patient, we are going to get to the interesting part
soon. Actually now.

Designing the main application window

Introducing glade

Open glade.
A quick description of what you see.

On the left section there is a list of widgets which you can drag
and drop in the middle section given that a widget can be placed there.
For example, you can’t add a top level window inside a label widget. I
will be calling this as the Widget section from now on.

On the middle section you see your widgets as they will appear
(most of the times) in the application. I will be calling this as the Design section from now on.

On the right section there are two subsections:

the top section contains the hierarchy of the widgets as added to the resource. I will be calling this as the Hierarchy section from now on.

the bottom section contains all the properties that you can
configure via Glade for a given selected widget of the aforementioned
top section. I will be calling this as the Properties section from now on.

I will try to describe the steps for building this tutorial’s UI
using Glade but if you are interested in building GTK+ applications you
should take a look at the resources & tutorials for using the tool
on the official page.

Create the application window design

We are going to create the application window. As you can guess, all
we have to do is drag the widget ‘Application Window’ from the widget
section to the design section.Gtk::Builder is an object used
in GTK+ applications to read textual descriptions of a user interface
(like the one we will build via Glade) and build the described
objects-widgets.
In the properties section, the first property is the ID and it has a default value applicationWindow1. If we let this property as is, then later on, through our code we would create a Gtk::Builder that would load the file produced by glade and in order to obtain the application window we would have to use something line:

The application_window object would be of class Gtk::ApplicationWindow
and thus whatever we had to add to its behavior (like setting its
title) would take place out of the original class. Also, as shown in the
snippet above, the code to connect to a signal of the window would be
placed inside the file that instantiated it.
Good news though, a GTK+ feature
introduced in 2013 allows the creation of composite widget templates
which among other advantages allows as to define the custom class for
the widget (which eventually derives from an existing GTK::Widget class
in general). Don’t worry if you are confused. You are going to
understand what is going on after we write some code and view the
results.
Now, in order to define our design as a template, check the Composite checkbox in the property widget. Note that the ID property changed to Class Name. Fill in there TodoApplicationWindow. This is the class we are going to create in our code to represent this widget.
Save the file with name application_window.ui in a new folder named ui inside the resources. If you open the file from an editor you will see this:

As you can see, our widget has a class and parent attribute.
Following the parent class attribute convention, obviously, our class
has to be defined inside a module named Todo. Before getting there, let’s try to start the application by executing the script (./gtk-todo).
Yeah! It starts!

Create the application window class

While running the application, if you check the contents of the application’s root directory you can see the gresource.bin
file there. Even though the application starts successfully because the
resource bin is present and it can register it, we do not use it yet.
We still initiate an ordinary Gtk::ApplicationWindow in our application.rb file and that all we show. Time to create our custom application window class.
Create a file named application_window.rb, place it under application/ui/todo folder and add the following content.

moduleTodoclassApplicationWindow<Gtk::ApplicationWindow# Register the class in the GLib worldtype_registerclass<<selfdefinit# Set the template from the resources binaryset_templateresource: '/com/iridakos/gtk-todo/ui/application_window.ui'endenddefinitialize(application)superapplication: applicationset_title'GTK+ Simple ToDo'endendend

We defined the init method as a singleton method on the class after opening the eigenclass in order to bind the template of this widget to the previously registered resource file.
Before that, we called the type_register class method which registers and make available our custom widget class to the GLib world.
Finally, each time we create an instance of this window, we set its title to GTK+ Simple ToDo.
Now, let’s go back to the application.rb file and use what we just implemented:

Define the model

For simplicity, we are going to save the ToDo items in files in json
format under a dedicated hidden folder in user’s home directory. Of
course, in a real life application we would use a database but this is
out of the scope of this tutorial.
Our Todo::Item model will have the following properties:

id: the id of the item

title: the title

notes: any notes

priority: its priority

creation_datetime: the date & time the item was created

filename: the name of the file that an item is saved to

Create a file named item.rb under the application/models directory, with contents:

require'securerandom'require'json'moduleTodoclassItemPROPERTIES=[:id,:title,:notes,:priority,:filename,:creation_datetime].freezePRIORITIES=['high','medium','normal','low'].freezeattr_accessor*PROPERTIESdefinitialize(options={})ifuser_data_path=options[:user_data_path]# New item. When saved, it will be placed under the :user_data_path value@id=SecureRandom.uuid@creation_datetime=Time.now.to_s@filename="#{user_data_path}/#{id}.json"elsiffilename=options[:filename]# Load an existing itemload_from_filefilenameelseraiseArgumentError,'Please specify the :user_data_path for new item or the :filename to load existing'endend# Loads an item from a filedefload_from_file(filename)properties=JSON.parse(File.read(filename))# Assign the propertiesPROPERTIES.eachdo|property|self.send"#{property}=",properties[property.to_s]endrescue=>eraiseArgumentError,"Failed to load existing item: #{e.message}"end# Resolves if an item is newdefis_new?!File.exists?@filenameend# Saves an item to its `filename` locationdefsave!File.open(@filename,'w')do|file|file.writeself.to_jsonendend# Deletes an itemdefdelete!raise'Item is not saved!'ifis_new?File.delete(@filename)end# Produces a json string for the itemdefto_jsonresult={}PROPERTIES.eachdo|prop|result[prop]=self.sendpropendresult.to_jsonendendend

As you can see, we defined methods to:

initialize an item

as new by defining the :user_data_path in which it will be saved later on

as existing by defining the :filename to be loaded from. The filename must be a json file previously generated by an item

load an item from a file

resolve whether an items is new or not (saved at least once in the :user_data_path or not)

save an item by writing its json string to a file

delete an item

produce the json string of an item as a hash of its properties

Add a new item

Create the button

Let’s add a button to our application window for adding a new item. Open the resources/ui/application_window.ui file in glade.

Drag a Button from the widget section to the design section.

In the properties section, set its ID value to add_new_item_button.

Near the bottom of the General tab in the properties section there’s a text area just below the Label with optional image option. Change its value from button to Add new item

Save the file and execute the script

Don’t worry, we will improve the design later on. Now, let’s see how to connect functionality to our button’s clicked event.
First, we have to update our application window class so that it learns about its new child, the button with id add_new_item_button. Then, we can access the child to alter its behavior.
Change the init method as follows:

definit# Set the template from the resources binaryset_templateresource: '/com/iridakos/gtk-todo/ui/application_window.ui'bind_template_child'add_new_item_button'end

Pretty simple, right? The bind_template_child method does exactly what it says and from now on every instance of our Todo::ApplicationWindow class will have an add_new_item_button method to access the related button. So, let’s alter the initialize method as follows.

As you can see, we access the button by the add_new_item_button
method and we define what we want to take place when clicked. Restart
the application and try clicking it. In the console you should see the
message OMG! I AM CLICKED every time you click the button.
What we want though to happen when we click this button is to show a
new window through which we will save a ToDo item. You guessed right.
Glade o’clock.

Create the new item window

Create a new project in Glade by pressing the most left icon of the top bar or by selecting File > New from the application menu.

Drag a Window from the widget section to the design area.

Check its Composite property and name the class TodoNewItemWindow.

Drag a Grid from the widget section and place it in the window we added in the previous steps.

Set its rows number to 5 and its columns number to 2 in the window that popped up.

In the General tab of its properties window, set its Rows spacing and Columns spacing to 10 (the numbers are in pixels).

In the Common tab of the properties section, set the Widget Spacing > Margins > Top, Bottom, Left, Right all to 10 so that the contents are not stuck to the borders of the window.

Drag four times a Label widget from the widget section and place them in each row of the Grid.

Change their Label property from top to bottom as:

Id:

Title:

Notes:

Priority:

In the General tab of the properties section, change the Alignment and Padding > Alignment > Horizontal property from 0.50 to 1 for each property. This will align the label text on the right.

This step is optional but I suggest that you do it: We will not
bind these labels in our window since we don’t need to alter their state
or behavior. So in this context, we don’t need to set a descriptive id
for each of them like we did for the add_new_item_button button in the application window. BUT. We are going to add more elements to our design and the hierarchy of the widgets in Glade will be hard to read with all the label1. label2. So set a descriptive id to each to make our lives easier (like id_label, title_label, notes_label, priority_label). I even set the grid’s id to main_grid cause I don’t like seeing numbers in ids or variable names :)

Drag a Label from the
widget section to the second column of the grid’s first row. The id is
automatically generated by our model thus we won’t allow editing so a
label to display it is more than enough.

Set the ID property to id_value_label.

Set the Alignment and Padding > Alignment > Horizontal property to 0 so that the text aligns on the left.

We are going to bind this widget to our window class so that we
can change its text each time we load the window so setting a label
through glade is not needed but doing so makes the design look closer to
what it’ll look like when rendered with actual data. So you can
optionally set a label here to whatever suits you better. I set mine to id-of-the-todo-item-here.

Drag a Text Entry from the widget section to the second column of the second row of the grid.

Set its ‘ID’ property to title_text_entry.
As you may have noticed, I prefer obtaining the widget type in the id
so that the code in the class becomes more readable later on.

In the Common tab of the properties section, check the Widget Spacing > Expand > Horizontal
checkbox and turn on the switch which is right next to it. This way,
the widget will expand horizontally every time its parent (a.k.a. the
grid) is resized.

Drag a Text View from the widget section to the second column of the third row of the grid.

Set its ID to notes. Nope, just testing you. Set its ID property to notes_text_view.

In the Common tab of the properties section, check the Widget Spacing > Expand > Horizontal, Vertical
checkboxes and turn on the switches which are right next to them. This
way, the widget will expand horizontally and vertically every time its
parent (a.k.a. the grid) is resized.

Drag a Combo Box from the widget section to the second column of the forth row of the grid.

Set its ID to priority_combo_box.

In the Common tab of the properties section, check the Widget Spacing > Expand > Horizontal
checkbox and turn on the switch which is right next to it. This way,
the widget will expand horizontally every time its parent (a.k.a. the
grid) is resized.

This widget is actually a drop down element and we are going to
populate its values that can be selected by the user when it shows up
inside our window class.

Drag a Button Box from the widget section to the second column of the last row of the grid.

On the popped up window select 2 number of items.

In the General tab of the properties section set the Box Attributes > Orientation property to Horizontal.

In the General tab of the properties section set the Box Attributes > Spacing property to 10.

In the Common tab of the properties section set the Widget Spacing > Alignment > Horizontal to Center.

Again, this widget won’t be altered by our code but you can give it a descriptive ID for readability. I named mine actions_box

Drag a Button widget twice and place it to each of the two boxes of the button box widget we added in the previous step.

Set their ID properties to cancel_button & save_button respectively.

In the General tab of the properties window, set their Button Content > Label with option image property to Cancel and Save respectively.

The window is ready. Save the file under resources/ui/new_item_window.ui.
Time to port it in our application.

Implement the new item window class

Before implementing the new class, we must update our GResource description file a.k.a. resources/gresources.xml to obtain the new resource:

Now we can create the new window class. Create a file under application/ui/todo named new_item_window.rb and set its contents as follows.

moduleTodoclassNewItemWindow<Gtk::Window# Register the class in the GLib worldtype_registerclass<<selfdefinit# Set the template from the resources binaryset_templateresource: '/com/iridakos/gtk-todo/ui/new_item_window.ui'endenddefinitialize(application)superapplication: applicationendendend

Nothing special here. We just changed the template resource to point to the correct file of our resources.
We have to change the add_new_item_button code that executes on the clicked signal to show the new item window.
Go ahead and change that code in application_window.rb to this:

Let’s see what we have done. Start the application and click on the Add new item button. Ta daaaaaaa
Of course, nothing happens when pressing the buttons. We will change that.
First we will bind the ui widgets in the Todo::NewItemWindow class.
Change the init method the to this:

definit# Set the template from the resources binaryset_templateresource: '/com/iridakos/gtk-todo/ui/new_item_window.ui'# Bind the window's widgetsbind_template_child'id_value_label'bind_template_child'title_text_entry'bind_template_child'notes_text_view'bind_template_child'priority_combo_box'bind_template_child'cancel_button'bind_template_child'save_button'end

This window is going to be shown either when creating a new Todo item or editing an existing one. Thus the new_item_window
naming is not very valid. This was intentional though so that we
refactor the code later (No it was not :D I made a mistake when writing
the tutorial. In any case, we’ll refactor later on).
For now, we will update the initialize method of the window to require one extra parameter, the Todo::Item
to be created or edited. We can then set a more meaningful window title
and change the children widgets to reflect the current item.
Change the initialize method to this:

and add the constant PRIORITIES in the application/models/item.rb file just below the PROPERTIES constant as:

PRIORITIES=['high','medium','normal','low'].freeze

What did we do here?

We set the window’s title to a string containing the id of the
current item and the mode depending on whether the item is now being
created or edited.

We set the id_value_label text to display the current item’s id.

We set the title_text_entry text to display the current item’s title.

We set the notes_text_view text to display the current item’s notes.

We create a model for the priority_combo_box whose entries are going to have only one String value. At a first sight, a Gtk::ListStore model might look a little confusing. I will try to explain how it works now.

Suppose we want to display in a combo box a list of country codes and their respective country names.

We would create a Gtk::ListStore
defining that its entries would consist of two string values: one for
the country code and one for the country name. Thus we would initialize
the ListStore as:

model=Gtk::ListStore.new(String,String)

In order to fill the model with data we would do something like this (make sure you don’t miss the comments in the snippet):

[['gr','Greece'],['jp','Japan'],['nl','Netherlands']].eachdo|country_pair|entry=model.append# Each entry has two string positions since that's how we initialized the Gtk::ListStore# Store the country code in position 0entry[0]=country_pair[0]# Store the country name in position 1entry[1]=country_pair[1]end

We also had to configure the combo box to render two text
columns/cells (again, make sure you don’t miss the comments in the
snippet):

country_code_renderer=Gtk::CellRendererText.new# Add the first renderercombo.pack_start(country_code_renderer,true)# Use the value in index 0 of each model entry a.k.a. the country codecombo.set_attributes(country_code_renderer,'text'=>0)country_name_renderer=Gtk::CellRendererText.new# Add the second renderercombo.pack_start(country_name_renderer,true)# Use the value in index 1 of each model entry a.k.a. the country namecombo.set_attributes(country_name_renderer,'text'=>1)

I hope I made it a little more clearer…

We add a simple text renderer in the combo box and instruct it to
display the one and only value of each model’s entry (a.k.a. position 0). Imagine that our model is something like [['high'],['medium'],['normal'],['low']] and 0 is actually the first element of each sub-array. I will stop with the model-combo-text-renderer explanations now…

Configure the user data path

Remember that when initializing a new Todo::Item (not an existing one) we had to define a :user_data_path
in which it would be saved. We are going to resolve this path when the
application starts and make it accessible from all the widgets.
All we have to do is check if the .gtk-todo-tutorial path exists inside the user’s home ~
directory. If not, then we will create it. Then we set this as an
instance variable of the application. All widgets have access to the
application instance. Sooooo….all widgets have access to this user path
variable.
Change the application/application.rb file to this:

One last thing that we have to do before testing what we have done so far is to instantiate the Todo::NewItemWindow when the add_new_item_button is clicked complying with the changes we made a.k.a. change the code in application_window.rb to this:

Note that we again close the window after saving the item.
Let’s try that out.
Pressing save and navigating to your ~/.gtk-todo-tutorial folder you should see a file there. Mine had the following contents:

{"id":"3d635839-66d0-4ce6-af31-e81b47b3e585","title":"Optimize the priorities model creation","notes":"It doesn't have to be initialized upon each window creation.","priority":"high","filename":"/home/iridakos/.gtk-todo-tutorial/3d635839-66d0-4ce6-af31-e81b47b3e585.json","creation_datetime":"2018-01-25 18:09:51 +0200"}

Don’t forget to try out the cancel button as well.
Awesome!!!

View ToDo items

We have left the Todo::ApplicationWindow to contain only one button. Time to change that.
We want the window to have the Add new item on the top but below it there should be a list with all of our todo items.
To accomplish that we are going to add a Gtk::ListBox in our design which can contain any number of rows.

Update the application window

Open the resources/ui/application_window.ui file in Glade.

If you try to drag a List Box
widget from the widget section directly on the window nothing happens.
That is normal. First we have to split the window in two parts. One part
for the button and one for the list box. Bear with me.

Right click on the new_item_window in the hierarchy section and select Add parent > Box.

In the popped up window, set that you need 2 items.

The orientation of the box is already vertical so we are fine.

Now, drag a List Box and place it on the free are of the previously added box.

Set its ID property to todo_items_list_box

Set is Selection mode to None since we won’t provide such a functionality.

Design the ToDo item list box row

Each row of the list box that we created in the previous step is
going to be more complex than a row of text. It is going to contain
widgets that will allow the user to expand an item’s notes, and to
delete or edit the item.

Create a new project in Glade as we did for the new_item_window.ui. Save it under resources/ui/todo_item_list_box_row.ui.

Unfortunately, at least in my version of Glade, there is no List Box Row
widget in the widget section so in order to add one directly as the top
level widget of our project, we will do it in a kinda hackish way.

Drag a List Box from the widget section to the design area.

Inside the hierarchy section right click on the List Box and select Add Row

Inside the hierarchy section right click on the newly added List Box Row which is nested under the List Box and select Remove parent. There it is. The List Box Row is the top level widget of the project now.

Check the widget’s Composite property and set its name to TodoItemListBoxRow.

Drag a Box from the widget section to the design area inside our List Box Row.

Set 2 items in the popped up window.

Set its ID property to main_box

Drag another Box from the widget section to the first row of the previously added box.

Set 2 items in the popped up window.

Set its ID property to todo_item_top_box.

Set its Orientation property to Horizontal.

Set its Spacing (General tab) property to 10.

Drag a Label from the widget section to the first column of the todo_item_top_box.

Set its ID property to todo_item_title_label.

Set its Alignment and Padding > Alignment > Horizontal property to 0.00.

In the Common tab of the properties section, check the Widget Spacing > Expand > Horizontal checkbox and turn on the switch which is right next to it so that the label expands to available space.

Drag a Button from the widget section to the second column of the todo_item_top_box.

Drag a Revealer widget from the widget section to the second row of the main_box.

Turn off the Reveal Child switch in the General tab.

Set its ID property to todo_item_details_revealer.

Set its Transition type property to Slide Down.

Drag a Box from the widget section to the reveal space.

Set its items to 2 in the popped up window.

Set its ID property to details_box.

In the Common tab, set its Widget Spacing > Margins > Top property to 10.

Drag a Button Box from the widget section to the first row of the details_box.

Set its ID property to todo_item_action_box.

Set its Layout style property to expand.

Drag two Button widgets to the first and second column of the todo_item_action_box respectively.

Set their ID properties to delete_button and edit_button respectively.

Set their Button Content > Label with optional image properties to Delete and Edit respective.

Drag a Viewport widget from the widget section to the second row of the details_box.

Set its ID property to todo_action_notes_viewport.

Drag a Text View widget from the widget section to the todo_action_notes_viewport that we just added.

Set is ID to todo_item_notes_text_view.

Uncheck its Editable property in the General tab of the properties section.

Create the ToDo item list box row class

Now we will create the class reflecting the user interface of the list box row which we just created.
First we have to update our GResource description file to include the newly created design. Change the resources/gresources.xml file as follows:

We will not bind any children at the moment here.
When starting the application, we have to search for files in the :user_data_path and for each file we must create a Todo::Item instance. For each instance, we must also add a new Todo::ItemListBoxRow to the Todo::ApplicationWindow’s todo_items_list_box list box. One thing at a time.
First of all, let’s bind the todo_items_list_box in the Todo::ApplicationWindow class. Change the init method as follows:

definit# Set the template from the resources binaryset_templateresource: '/com/iridakos/gtk-todo/ui/application_window.ui'bind_template_child'add_new_item_button'bind_template_child'todo_items_list_box'end

Next, we will add an instance method in the same class that will be
responsible to load the todo list items in the related list box.
Add this code in Todo::ApplicationWindow.

Note: We first make sure we empty the list box of
its current children rows and we refill it. This way, we will call this
method after saving a Todo::Item via the signal_connect of the save_button of the Todo::NewItemWindow and the parent application window will be reloaded! Here’s the updated code (in application/ui/new_item_window.rb):

in order to find all the names of the files that exist in the application user data path with json extension.
Let’s see what we’ve created. Start the application and try adding a new ToDo item. After pressing the Save button you should see the parent Todo::ApplicationWindow being automatically updated with the new item!
What’s left to do, is to complete the functionality of the Todo::ItemListBoxRow.
We will first bind the widgets. Change the init method of the Todo::ItemListBoxRow class as follows:

As you can see, when the details_button is clicked, we instruct the todo_item_details_revealer to swap the visibility of its contents.

After deleting an item, we find the application’s Todo::ApplicationWindow in order to call its load_todo_items as we did after saving an item.

When clicking to edit a button, we create a new instance of the Todo::NewItemWindow passing as item the current item. Works like a charm :D

Finally, we had to reach at the application parent of a list box row so we defined a simple instance method application that navigates through the widget’s parents until it reaches a window from which it can obtain the application object.

Save and run the application. There it is.
This has been a really long tutorial and even though there are so many items that we haven’t covered I think we better end it here.
Long post, cat photo.